Recent studies suggest that protein phosphorylation may play an important role in viral infection, replication, and/or assembly. Several animal viruses are known to contain phosphoproteins in their virions. Furthermore, protein phosphokinase activity has been demonstrated in numerous viruses, suggesting that the kinase, in addition to other enzymes, may also be a viral component. Although we have previously shown that adenoviruses do not contain any phosphokinase activity, the possibility that certain of the viral-associated polypeptides may be phosphorylated has not been investigated. Attempt will be made to determine whether adenoviruses contain protein-bound phosphate. This study may be carried out by growing adenovirus in P32-orthophosphate. The polypeptides of the purified P32-labeled virus will be fractionated by NaDodSO4-polyacrylamide gel electrophoresis; and the phosphopeptides identified by radioautography. The virus will be grown in different hosts in order to ascertain whether the host may cause a variation in the phosphorylation pattern. The enzymology of viral phosphorylation-dephosphorylation will also be investigated. Attempts will be made to purify the protein kinase and phosphoprotein phosphatase from infected and uninfected cells. The phosphorylation and dephosphorylation of animal viral proteins by these purified enzymes will be investigated.